1. Field of the Invention
This invention relates to an apparatus for collecting platelets from blood.
2. Description of the Related Art
The blood component collection is prevailing at present in the field of blood collection by such reasons as for effectively utilizing blood and reducing the donor's burden. This blood component collection comprises separating collected blood as by means of centrifugation into the blood components, isolating such a blood component as is necessary for a prospective donee, and returning the rest of blood components to the donor. When the blood component collection is aimed at producing a pharmaceutical preparation using a specific blood component, it adopts a procedure which comprises introducing the blood collected from the donor into a platelet collecting circuit and separating it by means of a centrifugal separator called a centrifugal bowl and disposed in the platelet collecting circuit into blood plasma, leukocytes, blood platelets, and erythrocytes. Of these blood components, the platelets are recovered in a container and used as a raw material for the platelet preparations, part of the plasma is also recovered in a container and used as a raw material for the plasma preparations or plasma derivatives, and the remainder of plasma, the leukocytes, and the erythrocytes are returned to the donor.
As a conventional platelet collecting apparatus, WO94/25086 (Publication of Unexamined Japanese Patent Application No. JP-A-08-509403), for example, discloses an apparatus for exalting the purity and the yield of platelets separated from the donated whole blood in a centrifugal separator. By this apparatus, the whole blood in the centrifugal separator is diluted at a first flow rate with such a circulating liquid as plasma or physiological saline water and further mixed before entering the centrifugal separator with the whole blood which will be subsequently collected. The plasma is circulated at a second flow rate through the centrifugal separator. Consequently, the separation between the intermediate density components in the buffy coat, namely the platelets and the leukocytes, is enhanced. Then, the plasma is circulated at a third flow rate through the centrifugal separator. While the plasma is being circulated at the third flow rate, the platelets emanate from the centrifugal separator. This procedure is intended to exalt the purity and the yield of the platelets separated from the donated whole blood. This apparatus, however, is at a disadvantage in incurring an unduly high cost of production and entailing an addition to the size of equipment because it necessitates use of three pumps, i.e. a blood collecting pump, a circulating pump, and an anticoagulant pump.
EP 0992256 A2 (Publication of Unexamined Japanese Patent Application No. JP-A-2000-107279) discloses a blood component collecting apparatus which, owing to decreasing the number of pumps to two, attains reduction in size of the apparatus, allays possible contamination of leukocytes, and allows high efficiency in the collection of platelets. This blood component collecting apparatus is furnished with a blood pump, an anticoagulant pump, a centrifugal separator driving unit, a plurality of flow path switching means, and a controller for controlling the operations of the two pumps, centrifugal separator driving unit, and plurality of flow path switching means. In this apparatus, the controller controls the operations of the two pumps, centrifugal separator driving unit, and plurality of flow path switching means and the subsequent processing steps are executed sequentially. To be specific, the plasma collecting step for collecting the blood incorporating therein the anticoagulant by actuating the blood pump and the anticoagulant pump and collecting the plasma into a plasma collecting bag by actuating the centrifugal separator driving unit; the constant rate plasma circulating step for suspending the blood collection and circulating the plasma in the plasma collecting bag to the centrifugal separator; the second plasma collecting step for actuating the centrifugal separator driving unit and collecting the plasma; the accelerated plasma circulating step for suspending the blood collection and circulating at an accelerated rate the plasma in the plasma collecting bag; the platelet collecting step; and the blood returning step are executed.
Publication of Unexamined Japanese Patent Application No. JP-A-2000-84066discloses a platelet collecting apparatus which is intended to exalt the efficiency of collection of platelets despite the use of three pumps. This apparatus increases or decreases the rotational frequency of a centrifugal separator or a circulating pump in conformity with the donor's hematocrit value. This apparatus, however, maintains the rotational frequency of the centrifugal separator constantly at a fixed level between the time the blood incorporating therein the anticoagulant is collected in the centrifugal separator and the time the platelets in the centrifugal separator are collected into the platelet collecting bag. The apparatus, therefore, is at a disadvantage in compelling the blood components (particularly the erythrocytes) separated in the centrifugal separator to be excessively compressed.